HLA-DR residues accessible under the peptide-binding groove contribute to polymorphic antibody epitopes

Many residues involved in polymorphic antibody-binding epitopes on class II molecules are located on the -helix of DRβ chains. Although they have received less attention, residues in the peptide-binding groove and second domain of the DRβ chain may also be critical for polymorphic anti-DR antibody epitopes. In this study, we used transfectants expressing site-directed mutations at positions in the HLA-DR β₁ and β₂ domains and flow cytometry to define the epitopes of several polymorphic anti-DR antibodies. Both DR(β 1^*0403) residues 14 and 25 were shown to be involved in the epitopes of mAbs DA6. 164, HU-20, Q5/6, and 50D6, and DR(β 1^*0701) residue 14 was shown to be critical for the epitopes of two DR7-specific mAbs, SFR16-DR7M and TAL 13. 1. Unlike most other residues shown to be important in antibody-binding epitopes, residue 14 is located in the floor of the peptide-binding groove and residue 25 is in an outer loop, each with their side chains pointing down, such that antibodies may directly contact these residues from below the binding groove. Two residues in the β₂ domain, β180 and β181, were also shown to be involved in the epitopes of three polymorphic anti-DR mAbs, NFLD.D1, NFLD.M1, and LY9. Although these two residues are close to the transmembrane domain in the linear sequence, their solvent accessibility in the DR1 structures is quite impressive. Our data provide new evidence that residues accessible under the peptidebinding groove contribute to polymorphic antibody-binding epitopes.     

Pathogenesis of infectious bronchitis nephritis. 2. Studies of water and electrolyte balance in colostomised chickens

Water and electrolyte balance was examined throughout the course of an experimental infection with T strain infectious bronchitis virus in colostomised chickens. Significant losses of water and negative sodium and potassium balances were observed. The major change in the electrolyte balance was the increased output of sodium in urine and this was associated with a diuresis. A decrease in food intake was the most important contribution to the negative potassium balance. Death resulted from acute renal failure. The implication of the results for electrolyte replacement therapy is discussed and a method for colostomies in birds weighing less than 0.5 kg is described.     

The influence of experimental distemper infection on the distribution of lead in dogs previously subacutely intoxicated with lead carbonate.

The ability of experimental canine distemper infection to mobilize body lead deposits has been studied in Beagle dogs previously subacutely intoxicated with lead carbonate. For comparative purposes dogs were included which had either received lead only or distemper only or remained undosed. It was found that in dogs predosed with lead, distemper infection resulted in a significant increase in lead levels in blood and urine; this coincided with the peak body temperatures reached on the third day post infection. It was also found that the lead content of the liver and bone of these dogs was considerably higher than that of dogs receiving lead alone; at the same time bone phosphorus showed a marked decrease while bone calcium values remained similar to undosed controls.